Refractory concrete and method of making



Patented June 13, 1950 umren stares- BATE-NI OFFICE amass I numerou cmscanrn AND METHOD OF Frank 11: Ls a xii. South .B aiuiic d. N. s-

signor to Universal Atlas (jement Company, a

edrporation of Indiana ruins. Arct the Se tember .5. fist asts 1s Glaims. (0i.

This inventi n r ate to an impr d et actory, e pa la l a e ractor c sisten which an e ti com o ent s c ium s at cement.

b'ng the bje s of he invention is th prcyisi u of a imp o d ef ac o pm sitipn yielding articles such as refractory structures and i shape of im r ved st en th a e ed t mp tu s. and 9 t rei qts shape 9i l s Iran: u comp s on- A further object of the invention resides in. e methpd by hich h o ed 're raetq structures and shapes composed of such improved refractory composition are made.

These and further objects of the invention will be more readily apparent in the following description of preferred modifications of the in-rvention.

The present invention represents improvements in certain aspects of the teachings of 'Kocher Patent No. 2,416,701, issued March 4, 19.47 it involves the discovery that improved properties in refractory concretes of the type referred to in that patent which contain as essential components calcium silicate cement and topaz, and preferably a. filler in the form of an aggregate, may be secured by the addition to such mixes of free silica? in finely divided form withinthe limits and in the manner below specified.

The refractory concrete of the present invention, which may be employed for applications such as those mentioned in the Koche'r p nt. is

made from a mix, the constituents of which lie within the same -broad limits as those given by Kocher with the addition, however, .cf finely divided free silica o silica flour, 1. .e.. u sand 15. y we g t of the total mix. The mix thus has the following composition, the components being given by per .cent of the total weight .of the mix' Per cent Topaz, raw or mrtly calcined. .426- -94.6 Calcium silicate cemen 4526 49.7 Refractory filler 9 9;4.i

Added free silica. 6.5 -15.0

It is preferred for some applications the added silica lie within thelimits 2.0 to 12.0% by weight of the total mix. In such preferred mix the components are present in the following amounts:

e ent opa 4.. 3- Calcium silicate cement 4.49 ..--58.8 Ref actory fi ets.--,- 0 Added free silica-----, --P.-----, 2.0 43.0

Ftters flint within the range .of mm 30.5 to

. acce era 5 calcium sulfate. The following Portland cement I typical;

' r cen E? SiOa r-rrr-r M293 FezOa Up to 4.5

Mae, aikalies and minor constituents-l, liia lan cfe El e Portl a.nd-.b last furnace sla cement,.' as that te m .su e re ma 8 y erm ne i se er Por l n ceme i igr' andsral u aied -"Portland pozzuolan cements, that.

.e. n, a e P o. y ri di g it ther .?25-, :P.Sl-.3 lll2 slil ukf end either a natural-'or'artificial ozzuolana'.

'1'E e true ozzuolanic cements," as that term ussdh xe a e co os d of Time nd r nusla such as v cin e or blast fur inace s g, mixed without heating. ypica semen. thi t pe i m mixing y mated e with slag from an iron blast furnace, sax sag Vav i ng been quenched suddenly in water to leave the slag in a glassy non-crystalline form. The resultinglime-slag mixture is ground to a fine. powder and is then-ready for use.

The slag cement, as that term is used herein, is a mix ure of hydrated lime and granulated blast 11/ CROSSREFEREMCE furnace slag. Certain additions may be added to e set.

The natural h draulic cements," as that term is used Herein, are those made ByTalcining argillaceous limestones at temperatures only so 3 as o expe e combined C02 and H20. The calqareous portion of such argillaceous limestones may consist of CaCOa essentially, or of gs. andlgg carbonates com'Ei'fie'd' in various proportions up to 8., represented by the mineral dolomite, CaMg (C03) 2.

By artly calcined topaz as used above is 433.6 meant a tTwpaz which Has Been heated in such manner that at least 1% by weight of its maximaceous earth, crushed red-hr ck and the 1 The constituents of the mix are supplied thereto in either comminuted or granular form to allow them to be uniformly distributed throughout the mix and consequently the resulting concrete. Those constituents which form the bond are preferably finely ground to facilitate their reaction. The calcium silicate cement, for example, may be of such fineness that practically all particles will pass through a 100 mesh screen, and the tops! may be ground toany particle size. It is preferred thatthe added silica likewise be finely ground, for example, to a particlesiz'e comparable to that of the cement, although it is to be understood that such particle size of the added silica is capable of considerable variation. The refractory filler or aggregate may be of any desired particle size or range of particle size consistent with substantial uniformity of distribution through the resulting concrete. The particle size of the aggregate naturally will be chosen with the minimum section of the shape or structure to be made in view.

The mix may conveniently be made by mixing the calcium silicate cement, the tofiz, and the added free s1 ica ry co dition to a uniform color, the refractory aggregate being thoroughly wet down with wa r and then added to the mixture of the calcium silicate cement, topaz, and the added free silica. Suflicient water is added to the resulting mixture to render it workable, the amount added depending upon the manner in which the mix is to be subsequently handled inthe formation of the concrete shape or structure. Thus, if the concrete is to be cast into a mold or form, particularly if the shape is intricate, the mix should be of puddling consistency. For simple shapes, so cast, less water may be used, whereas if the mix is to-be tamped or'vibrated into place or molded under pressure, still less water may be used. It is obvious that su mcient water should be used in all cases to develop fully the hydraulic strength of the cement and that an excess of water should be avoided. Besides the variations 'in modes of handling the mlxabove indicated, it

is possible to deposit it in a mold or form or in any desired location, as for instance, in the applying of patches to existing structures, by charging the mix into a cement gun which pumps or otherwise forces it out through a discharge orifice.

After the mixture has been shaped or molded in 4 any one of the ways above described, it is dried and then heated. Usually for bodies of large section, suchafi'fst furnace walls, the practice follows approximately that employed in the drying 6 and heating of newly constructed firebrick linings.

The concrete may be air dried for a period of several days, after which the furnace is heated at temperatures which gradually increase up to operating temperature.

Small bodies and shapes, such as cast bricks,

tiles and slabs may be kept for a time, on the order of at least seventy-two hours in a high humidity-constant temperature atmosphere, dried at a low temperature, on the order of 230 F., and

then subjected to a high temperature approximating that at which the shape will be used, for example 1600-2000 F.

Concrete resulting from mixes made in accordance with the present invention after having been dried and heated as above possesses increased strength, as compared to similar concretes similarly treated, both made without topaz and added silica, in accordance with the prior art, and containing topaz but no added free silica, in accordu ance with the teaching of the aforementioned Kocher patent.

Such increased strength of the concrete of the present invention at room temperatures are shown by the results set out by the following Tables I and 11 giving the compressive strengths of 2 inch cubes made of mixtures containing the indicated percentages by weight of Portland cement top az, regagt r y aggregate and added free silica in the form of silica Hour. In the making of vsucfi 2 inch test cubes the mix was made of a puddling consistency and poured into 2 inch cube molds. After being cured for seven days in a moist cabinet the cubes were dried at 230 F., fired for the indicated length of time at the indicated temperature, and were then allowed to cool. After cooling, each cube was subjected to a compressive strength test at room temperature by subjecting 'it to gradually increasing pressure until a point of failure of the cube was reached.

.InTable I, below, the mixes employed con-"- tained Portland cement, topaz, olivine, and silica flour, whereas e m es employe contained Portland cement, topaz, crushed firebrick and silica flour. The Portland cement '50 all test was ground to a size such that 11.0%

remained on a 326 mesh sieve. The silica flour was ground to pass a 100 mesh sieve and the olivine and crushed firebrick ranged in particle size from inch to dust. Each of the values given for each test in the following Tables I and 11 represents the average of tests on three similar 2 inch cubes. The figures under each heading in the tables represent the per cent of such material in the total batch by weight.

TABLE I Portland cement-Olivine aggregate Compressive Stren th lbs. per Sq. Inch Fire 4 Days Cement Olige Topaz Percent Percent Percent Percent 1 18.9 81.1 666 508 473 2 16. 0 68. 0 16v 0 650 446 1, 694 3 15.7 66.7 15.7 1.9 1,028 542 1,608 4 16.4 85.6 16.4 3.8 1,216 638 1,975 5 14.8 63.0 14.8 7.4 1, 820 1,467 2,096 6 14. 3 60. 7 14. 3 10. 7 1, 796 1, 704 2, 479 7 13.8 58.0 13.8 13.8. 1 1,909 1, 520 2,350

r a I in Tam LdiUbh liti'ili'itliiit TABLE If." Portland cement-am firebricla f Compressive Strength, lbs.- perSq. Inch Fired LDaye 'Cement 'Firebrick Topaag gg ff Q "mo n. meow. meow.

Percent Percent I v 1 20.6 n4. e81 470 605 2 17.1: baa 11.1 1,101 1,892 2,232; 3 16.8, 1.64.3 16.8 2.1 1,408 m 2661 4- 16.4 03.1- K 16.4' at 1,700 725 m 6 as sa- -.l-2 E 1 7 we as: 14.1; t IL in zinc 41m It'- will be noted that Table I shows a material increase in compressive strength of olivine-Portland cement-topaz mixtures, when fired at 1600 F. and 1800 F., the strength of specimens fired at 2000 F. remaining about the same, when as little as 1.9% finely divided free silica is added to the mix. The strength of specimens fired at all three given temperatures increases, with increased added silica, until 13.8%silicai's added at which point the strengths of specimens fired at 1800 F., and 2000 F. drops off slightly.' It is to be understood, however, that the-invention is not to be restricted to the typical specimens given by way of example, and that the invention includes the addition of. from 0.5 to 15.0% by.

weight of the mix of finely divided free silica, the preferred rangeof such addition being from 2.0 to 12.0%-

Table II shows the results of adding from 2.1 to 14.6% by weight of the mix of finely divided free silica to various crushed firebrick-Portland cement-topaz mixtures. .Witlr' such mixtures increases in compressive strengths over those of specimens of test No. 2, which contained no added free silica, are obtained at all temperatures of firing within the range of added free silica shown in the table. Here again, however, it should be emphasized that such mixtures are illustrative only, and that the invention includes the addition of finely divided free silica within the broad and the preferred ranges set out above to the specified mixtures containing calcium silicate cement.

The reason why refractory concretes employing calcium silicate cement and topaz with free silica added thereto in accordance with the present invention possess increased hot and cold strengths as compared to similar concretes without the added free silica is not fullyunderstood. The theory which seems most fully to accord with the facts as now known is that the added silica which, of course, is free silica and is of the particle size such that it readily reacts with other components of the bond, is acted upon by the fiuo ine or released upon heating of the topaz to form afid in which silica plays a large part, such silica being either silica per se in crystalline form or combined with alumina to form mullite in fine crystalline form. The improvement in strength of concretes by such addition of free silica appears most marked with aggregates containing little or no free silica.

Regardless of the correctness of such theory, it is possible to employ the present invention with concretes containing the added free silica but in which the topaz is not present in the mix, the concrete being subjected to the volatile roducts released b to az when heated in proximity fi'tfl''oncrete. The various methods by which concrete may be subjected to such volatile products of topaz have been set out in the above smaller shapes, such as bricks, slabs, and tiles,

by heating suchshapes in a muffle furnace with a quantity of topaz in a crucible likewise placed in the muflle furnace. With larger shapes such as furnace walls and the like, the furnace or other part may be heated preparatory to being placed in service and thereafter subjected to the action of an atmosphere of volatile products of topaz. Such improvement instrength inrefractory concrete containing calcium silicate cement, refractory aggregate, and added free silicate within the limits noted, may also be attained after'the concrete has been in service by the diffusion into it at elevated temperatures of the volatile products given of! by topaz when heated to at least 1400" R, such heating of the body and the topaz adjacent thereto preferably being carried out at temperatures of at least 1600 F. Whereas particular embodiments of the invention have been described above for purposes of illustration, it will be evident that numerous variations of details are possible within the teaching of the invention. I desire to claim as new the following.

I claim:

1. A mix for forming refractory concrete comprising the following components by weight of theymix: calcium silicate cement from 4.26 to 59.7%, topaz containing from 1 to 17.4% by weight of fluorine from 0.426 to 94.6%, and silica flour from 0.5 to 15.0%.

2. A mix for forming refractory concrete comprising the following components by weight of the mix: calcium silicate cement from 4.40 to 58.8%, topaz containing from 1 to 17.4% by weight of fluorine from 0.44 to 93.0%, and silica flour from 2.0 to 12.0%. 3. A mix for forming refractory concrete comprising the following components by weight of the mix: silicate cement from 4.26 to 59.7%, topaz containing from 1 to 17.4% by weight of fluorine from 0.426 to 94.6%, refractory aggregate from 1 to 94.1%, and silica flour from 0.5 to 15.0%.

4. A mix for forming refractory concrete comprising the following components by weight of the mix: Portland cement from 4.26 to 59.7%, topaz containing from 1 to 17.4% by weight of fluorine from 0.426 to 94.6%, refractory aggregate flrsog y 1 to 94.1%, and silica flour from 0.5 to

5, A mix for forming refractory concrete comprising the following components by weight of the mix: Portland cement from 4.40 to 58.8%, topaz containing from 1 to 17.4%, by weight of fluorine from 0.426 to 94.6%, refractory aggregate from 1 to' 92.6%, and silica flour from 2.0 to 12.0%.

6. A refractory concrete formed from a mix comprising the following components by weight of the mix: calcium silicate cement from 4.26 to 59.7%, topaz containing from 1 to 17.4% by weight of fluorine from 0.426 to 94%, and silica flour from 0.5 to 15.0%.

7. A refractory concrete formed from a mix comprising the following components by weight of the mix: calcium silicate cement from 4.26 to 59.7%, topazcontaining from 1 to 17.4% by weight of fluorine from 0.426 to 94.6%, refractory aggregate from 1 to 94.1 and silica .fiour from 0.5 to 15.0%.

8. A refractory concrete formed from a mix comprising the folowing components by weight of the mix: calcium silicate cement from 4.40 to 58.8%, topaz containing from 1 to 17.4% by weight of fluorine from 0.44 to 93.0%, and silica flour from 2.0 to 12.0%.

9. A refractory concrete body formed from a mix comprising the following components by weight of the mix: Portland cement from 4.26 to 59.7%, topaz containing from 1 to 17.4% by weight of fluorine from 0.426 to 94.6%, refractory aggregate from 1 to 94.1%, and silica flour from 0.5 to 15.0%.

10. The method of making refractory concrete which comprises heating a body made from a mix comprising the following components by weight of the mix: calcium silicate cement from 4.26 to 59.7%, and silica flour from 0.5 to 15.0%, and subjecting such body to contact with the fluorine given 011 by the heating of topaz at a temperature of 1600 1. v

11. The method of making refractory concrete which comprises making a mix comprising the following components by weight of the mix: calcium silicate cement from 4.26 to 59.7%, refractory ag regate up to 94.1 and silica flour from 0.5 to 15.0%, hydrating the mix and producing therefrom a concrete body, installing such body for service, and in the initial firing of the body subjecting it to contact with the fluorine given off by topaz when heated to 1600 F.

12. The method of treating a refractory concrete body formed from a mix comprising the following components by weight of the mix: calcium silicate cement from 4.26 to 59.7%, re-

fractory aggregate up to 94.1% and silica flour from 0.5 to 15.0%, which comprises heating said body and subjecting it to contact with the fluorine given off by topaz when heated to 1600 F.

13. The method of making refractory concrete bodies which comprises making a mix comprising the following components by weight of FRANK E. LOBAUGH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,416,701 Kocher Mar. 4, 1947 Certificate of Correction Patent No. 2,511,725 June 13, 1950 FRANK E. LOBAUGH It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 7, line 4, for 0.426 to 94.6% read 0.44 to 93.0%; line 10, for 94% read 94.6%;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 12th day of September, A. D. 1950.

THOMAS F. MURPHY,

Assistant Oommz'ssz'aner of Patents. 

1. A MIX FOR FORMING REFRACTORY CONCRETE COMPRISING THE FOLLOWING COMPONENTS BY WEIGHT OF THE MIX: CALCIUM SILICATE CEMENT FROM 4.26 TO 59.7%, TOPAZ CONTAINING FROM 1 TO 17.4% BY WEIGHT OF FLUORINE FROM 0.426 TO 94.6%, AND SILICA FLOUR FROM 0.5 TO 15.0%. 